Refining of fatty oils



Patented July 1, 11941 Zfidtutliil REFIINING @F FATTY OHIS Arthur U. Ayres. dihestnut Hill, lPa, assignor to The Sbarples Corporation, Philadelphia, la., a

corporation of Delaware No Drawing. Application December 27, 1938,

Serial No. 247,333

l2 @ialms.

The present invention relates to the refining of vegetable and animal oils. It was conceived in connection with problems arising in the refining of oils of the type of co'coanut and babasu oils, but it is applicable also to the refining of other fatty oils.

Oils of the type of cocoanut and babasu are ordinarily refined substantially as follows, The oil to be refined is placed in a large kettle, heated, and treated with an alkaline solution containing more than a molecular equivalent of alkali based upon the fatty acid content of the oil. The oil is vigorously agitated with the alkaline solution by means of a mechanical agitator until a condltiOn of break occurs; l. e., until the soap stock particles begin to agglomerate. The oil is then allowed to stand in a heated condition for a considerable period 01' time, water often being sprayed upon the surface of the oil inorder to facilitate settling of the soap stock. During this prolonged standing the soap stock settles toward the bottom of the refining kettle.

The steps of spraying the alkali treated oil with water and settling do not efi'ect a complete subsidence of soap stock from the body of the oil, and the oil layer from which the bulk of the soap stock has subsided therefore contains a. considerable proportion of unseparated soap stock. This dispersed soap stock is ordinarily later re- .moved from the oil by filtration or bywsshing with water.

If the soap stock is'to be removed from the oil by filtration itis customary to draw of! the oil. by means of a heating arm, from the main body of soap stock which has subsided through that oil. In drawing on. the oil in this manner the refiner must be careful not to draw ofi the soap stock which has stratified from the oil by subsidence, for attempts to filter 011 containing a large proportion of soap stock result in rapid cloggage of the filter presses used in the filtering operation and in a decrease in the emciency of the operation of filtration, with the consequence that even the filtered oil contains an undesirably high proportion of soap, and losses are high, due to frequent press cleaning.

In view of the deleterious eflects encountered in attempts to filter soap stock from oil containing a high proportion of soap stock, as discussed above, it is customary for the refiner, to take careful precautions to avoid decanting from the kettle a mixture or oil and soap stock containing the oil decanted from the subsided soap stock is.

plete the refining operation.

In an alternative method of procedure practhereafter passed through a filter press to com- I ticed by refiners in accordance with the prior art.

' the oil is mixed with alkali, heated and, if necessary, sprayed with water as described above, the treated oil is then drawn off from above the soap stock layer and delivered to another tank where it is washed with water and allowed to settle. When this procedure is adopted, the operator must take care to avoid removal of any substantial proportion of the subsided soap stock layer with the decanted oil, just as in the case of oil which is subsequently treated by filtration, The reason that this precaution must be taken lies in the fact that when the water washing and subsidence separating operations are performed in the second tank upon a mixture of oil and soap stock containing substantially over 0.2% soap stock, an emulsion is iormedin the water washing tank which cannot be adequately separated into its constituents by gravity settling. Another dimculty which arises in the process last described consists in the fact that a considerable quantity of refined oil is lost with the wash water. A still further dimculty encountered in connection with the water washing process last described consists in the fact that the water washed 1 oil contains a considerable quantity of moisture.

such removal is not thorough for the depth 01! the oil in the tank is suficiently great to partially nullify the vacuum and prevent adequate removal of the water from the lower part of the tank.

By the process of the present invention all of the above described difilculties encountered in the twoalternative prior art processes are obviated. Anobject of the present invention has been to provide a process resulting in a substantial increase in the yield of refined oil as compared to these prior art processes. In one embodiment of the present invention, the oil is refined in a refining kettle by mixing it with an alkaline solution, heating spraying with water if necessary,

and subjecting the mixture to gravity subsidence Just as described above in connection with the .prior art processes. This results in the formation is continuously discharged from this drying apof deep layer of oil containing a relatively small proportion of soap stock and an underlying layer of soap stock containing some 011 just as in the case of the conventional process described above. At the conclusion of the alkali treating, spraying, and agitating operations described above, the operator decants from the concentrated underlying layer of soap stock the bulk of the oil contained in the kettle and also a part of the mixture of oil and soap stock underlying that oil. By reason of the novel combination of steps follow- 1118 this step of decantation of the oil from the bulk of the soap stock, the refiner practicing the present invention, instead of being required to exercise great care to avoid high concentration of soap stock in the oil, may decant from the bulk of the soap stock, oil and soap stock in proportions such that the mixture of decanted material con.-

tains between 0.2% and 1% of soap stock; 1. e., he may produce a mixture of oil and soap stock.

containing as much as 5 times the soap stock which can be efliciently treated in accordance with the prior art processes. The result of this the present invention is salvaged.

After the decantation of the mixture of the oil and soap stock from the bulk of the soap stock as above described. the separated mixture of oil and soap stock is thoroughly agitated to produce a uniform dispersion of the soap stock (constituting for example 0.7% based upon the volume of the oil) in the oil. The mixture of oil and soap stock so produced" is then thoroughly agitated with 1 water and subjected to centrifugation to remove water and soap stock from the oil are preferably accomplished rapidly and continuously by feeding the mixture of oil and soap stock into, confluence with water, thoroughly mixing the mixture or oil and soap stock with the water. continuously heating the mixture to a temperature between M0 and 180 F. and passing the mixture to a centrifugal separator which resolves the mixture into a heavier stratum of soap stock and water on the one hand and a light stratum of oil on the other hand and continuously discharges the respective strata. The wash water is preferably separated from the oil within a few minutes after the mirrture is contacted with water.

The oil discharged from the centrifugal separator still contains a'certain amount oi water and may contain a small proportion of soap stools.

The continuous water washing operation may be repeated on the oil discharged from the primary centrifugal separator to remove residual traces of soap stash if necessary, and in the preferred centrifuge is promptly injected through nozzles into a vacuum drying apparatus and the oil which has been suhstantialiy freed of soap and moisture paratus.

The advantages'of the invention will be evident from the above description. By treating a mix ture of oil and soap stock from the refining kettle which contains. a substantially higher proportionof soap stock than that treated in accordance with the filtering and water washing steps of the prior art processes, the oil associated with the additional soap stock so treated is salvaged. But if an attempt were made to treat a mixture containing this. additional soap stock with its entrained oil in accordance with prior art processes, great diiiiculties would be encountered in the filtering or water washing operation. These difiiculties are obviated in the practice of the present invention by the application of centrifugal force in that operation, since the centrifugal separator affords a means of separatingthe oil from the emulsion of water and soap stock which is many thousand times more powerful than the force of gravity.

, While the invention has been described in connection with an operation in which the mixture of oil and soap discharged from the refining kettle is washed with water, it will be understood that water containing salting out agents may be substituted for pure water in this washing operation, or that such salting out agents (e. g., sodium chloride, sodium sulphate, sodium silicate, trisodium phosphate or equivalent reagent) may be added separately to the oil or to the mixture of oil and water to facilitate the separation incident to the washing operation. By adding a salting out agent, in solution in the water or otherwise, it is possible to treat a mixture of oil and soap stock containing as much as 1.5% of soap stock and eflect removal of such soap stock in one or more washin rations.

While the invention has been described in connection with the treatment of cocoanut oil and babasu oil. it will be-understood that it is not limited totreatment of these specific oils. Indeed, the invention may be applied to the treatment of a wide variety of fatty oils'with advantageous results in the form of increased yields obtained in the refining operation. The invention therefore comprehends within its broad scope the treatment of any fatty oil which may be refined with alkaline solutions as described herein.

While the invention has been described in conoil and soap stock is sprayed with water to facilitate subsidence of the soap stock through the oil, the water treatment may be omitted in case emcient subsidence can be obtained without such treatment and the invention is in no way limited to the performance of the step of spraying the mixture of oil and soap stock with water ri to subsidence. 1 p or The invention is not limited to any particular sequence or .w i and heatiugsteps to be performed in the refining operation or to any par,- tieular twperature or range of temperatures to he employedln such steps. Thus, within the broad scope of the invention the oil may be mixed with alkali before heating or heated before mixing with alkali, and the mimng and subsidence steps may be performed at a wide range of temperatures hetween 7c and F. or evenwithin a somewhat wider range. It is preferable. however, in the practice of the process to maintain a the oil at a sumcien'tly high temperature to ei= feet a 'hreels" at the time oi performance of the the oil; 1. e., to keep the oil at least as warm as the'conveutional emulsion breaking temperature which has always been employed by refiners for this step.

While the invention has been described with reference to the performance of the step of'mixing oil with alkali in the refining kettle and subsidlng the soap stock through the oil in this same kettle, these steps may be performed in separate apparatus if desired, and the process may be made continuous by continuously mixing the oil and alkali in one container and effecting continuous subsidence of oil from the soap stock in another piece of apparatus such as a settling tank or centrifugal separator. Thus the process may be practiced by continuously mixing the oil with alkali in a mechanical mixer and continuously passing the mixture to a centrifugal separator which causes subsidence of the soap stock to the inner wall of the centrifugal rotor. Oil containing finely divided soap stock may be continuously or intermittently discharged from this centrifugal rotor and a part of the soap stock containing entrained oil intermittently or continuously discharged separately and collected with the discharged oil to-produce a mixture of oil and soap stock containing between 0.2 and 1.5% of soap stock. This mixture may then be agitated to effect uniform dispersion of the soap stock in the oil and treated in accordance with the water washing and vacuum treating steps described above in connection with the treatment of kettle refined oil.

If the process is made continuous by mixing the oil with alkali and passing the mixture to a continuous settling tank or centrifugal separator as described above, the mixture of oil and soap stock in the continuous settling tank or, centrifugal separator may be sprayed with water to facilitate subsidence of the soap stock through the oil -just as in the case in which the soap stock is subsided from the mixture in the refining kettle. This spraying operation may be conducted in a centrifugal separator by introducing a spray nozzle into the center of the centrifugal rotor, or the oil may be sprayed before being passed to the centrifugal separator.

In the practice of the process involving centrifugation to cause subsidence of the soap stock through the oil, the oil and a part of the soap stock may be continuously separated from the bulk of the soap stock by adjustment of the conventional ring dams of a centrifugal separator or other conditions to deliberately discharge a soapy oil. A quantity of oil and soap stock containing between 0.2% and 1.5% soap stock may thus be continuously discharged as the lighter effluent while the bulk of the soap stock. is discharged as the heavier efiuent. The process of centrifugation can alternatively be performed by passing the mixture of oil and soapstock froms the refining kettle or any suitable form of mixer designed to mix the oil with alkali intermittently or continuously to a centrifugal rotor which operates to causethe soap stock to subside through the oil but does not discharge the oil and soap stock, phases underliquid balance against each other Thus the mixture may be spun in such a centrifugal rotor (and sprayed with water during the spinning if desired) and the oil and part of the soap stock thereafter removed by means of a dislodsing tool such as the conventional skimming nozzle during the rotation'of the rotor. After the removal of a mixture of oil and soap stock containing between As a still further alternative, the mixture of oil and soap stock produced as a result of the alkaline treatment of the crude oil. may be separated into separate eifiuents consisting respectively of a mixture of oil containing between.0.2% and 1.5% soap stock on the one hand'and the bulk of the soap stock on the other hand by means of a centrifugal separator provided with peripheral openings which are designed to continuously or intermittently discharge the soap stock. It will be evident from the above discussion that the invention may be practiced in a wide variety of forms. In every such form the essential feature and the feature by which the valuable results of the invention areachieved consists in the subsidence of soap stock from an alkali treated fatty oil, the treatment with the subsided oil of soap stock containing a substantial quantity of entrained oil and the centrifugal water washing of the mixture of soap stock and refined oil so separated from the bulk of the soap stock.

When reference is made in the subjoined claims to mixing oil and soap stock with water, I wish it to be understood that the term water is to be interpreted in a. generic sense as including not only pure water but also water which may contain any emulsion breaking agent, such, for example, as one of the salting out agents referred to above.

Modifications will be obvious to those skilled in the art, and I do not therefore wish to be limited except by the scope of the subjoined claims.

I claim:

1. The process of refining fatty oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and form soap stock, stratifying said soap stock from said oil, separating at least a part of said soap stock from said oil, mixing with water said oil from which at least a part of said soap stock has been so separated, mixing with said water and oil a substantial quantity of previously Stratified soap stock formed by said neutralization treatment and lying adjacent the oil stratum, and thereafter separating from the oil by centrifugal force soap stock and the water which has been admixed with said oil and soap stock.

2. The process of refining fatty oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and form soap stock, stratifying said soap stock from said oil, separating from said soap stock saidt'oil together with a part of the previously 'sftl atified soap stock lying adjacent the oil stratum, mixing with water the oil and soap stock so separated from the bulk'of. the soap stock,and'tliereafter separating from the oil by centrifugal force soap stock and the water which has been admixed 3. The process of refining fatty oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and form soap stock, stratifying said soap stock from saidoil,

separating from said soap stock said oiltogether with a part of the previously stratified soap stock lyingadjacent the oil stratum, agitating the oil and soap stock so separated from'the bulk of the soap stock to disperse the soap stock separated fromthe bulk of the soap'stock substantially uniformly-in the oil separated from soap stock from 4 of oil andsoap stock with water containing a the bulk of the soap stock, mixing the mixture of oil and soap stock formed by said agitation with water, and thereafter separating from the oil by centrifugal force soap stock and the water which has been admixed with said oil and soap stock.

4. The process of refining fatty oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and form soap stock, stratifying said soap stock from said oil, skimming said oil from said stratified soap stock, skimming a part of said previously stratified soap stock lying adjacent the oil stratum from the bulk of said stratifledsoap stock, mixing with water said skimmed oil and said skimmed soap stock, and thereafter separating from the oil by centrifugal force soap stock and the water which I has been admixed with said skimmed oil and said skimmed soap stock. I

5. The process of refining fatty oilswhich comprises mixing an alkali with the oil to be refined to'neutralize the free fatty acid and form soap stock, centrifugally stratifying said soap stock from said oil, separating at least a part of said centrifugally stratified soap stock from said oil, mixing with water said oil from which at least a part of said soap stock has been so separated,

mixing with said water and oil a substantial quantity of previously stratified soap stock formed by said neutralization treatment and lying adjacent the oil stratum, and thereafterseparating from the oil by centrifugal force soap stock and the .water which has been admixed with said oil and soap stock.

6. The process of refining fatty oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and form soap stock, stratifying said soap stock from said salting out agent during said centrifugal stratification to facilitate said stratiflcation, separating at least a part of said centrifugally stratified soap stock from said oil, mixing'with w'atersaid oil from which at least a part of said soap stock has been so separated, mixing with said water and oil a substantial quantity of previously stratified soap stock formed by said neutralization treatment and lying adjacent the oil stratum,

oil by centrifugal force in a centrifugal rotor,

continuously discharging from said centrifugal rotor oil from which said soap stock has been sostratified, continuously discharging with said .011 an amount of soap stock lying adjacent the oil stratum constituting between 0.2% and 1.5%

of the weight of said oil, mixing with water the oil and soap stock discharged together from the centrifugal rotor, and thereafter separating from the oil by centrifugal force soap stock and the water which has been admixed with said oil and soap stock. a

7. The process of refining fatty oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and form soap stock, centrifugally stratifying said soap stock from said oil, spraying the mixture of oil and soap stock with water during said centrifugal stratification to facilitate said stratification, separating at least a part of said centrifugally stratified soap stock from said oil, mixing with water said oil from which at least a part of said soap stock has been so separated, mixing with said ,water and ofl a substantial quantity of previously stratified soap stock formed-by s'aidyneutralization treatment and lying adjacent the oil stratum, and thereafter separating from the oil by centrifugal force soap stock and the waterwtgicckh has been admixed with said offend-soap s 8. The process of refining fatty" oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and oil together with a part of the previously, stratisoap stock from said oil, separately removing said stratified soap stock and said all from which said soap stock has been stratified from the influence of centrifugal force, re-mixing said oil removed from the influence of centrifugal force with a part of the'soap stock separated from the oil and separately removed from the influence of centrifugal force, mixing the mixture of oil and soap stock so formed with water,,and

thereafter separating by centrifugal force oil from the mixture formed by mixing said mixture of oil and soap stock with water.

10. The process of refining fatty oils which comprises mixing an alkali with the oil to be refined to neutralize the free fatty acid and form soap stock. stratifying said soap stock from said oil, separating at least-*a part of said soap stock from said oil, mixing with water said oil from which at least a part of said soap stock has been so separated, mixing with said water and oil a quantity of previously stratified soap stock formed by said neutralization treatment amounting to between 0.2% and 1.5% of the weight of the oil, and thereafter separating from' the oil by centrifugal force soap stock and the water which has been admixed with said oil and soap stock.

11. The process of refining fatty oils which comprises mixing an alkali with the oil to berefined to neutralize the free fatty acid and form soap stock, stratifying said soap stock from said oil. separating from said soap stock said fled soap stock amounting to between 0.2% and 1.5% of the'oil so separated, mixing with water the oil and soap stock so separated from the bulk of the soap stock, and thereafter separating from the mixture by centrifugal force soap stock and the water which has been admixed with said oil and soapstock.

'12. The process of refining fatty oils which comprises mixing an alkali with the oil to be form soap stock, centrifugally stratifying said said oil, @reyingthe mixture 'haebeenedmixedwith refined to neutralize the free fatty acid and form soap stock. stratifying said soap stock from said oil, separating from said soap stock said oil together with a part of the previously stretified soap stock amounting to between 0.2% and 1.5% of the oil so separated, agitating the oil and soap stock so separated from the bulk of the soap stock to disperse the soap stock separated from the bulk .of the soap stock substantially uni formly in the'oii separated from the bulk of the soap stock, mixing with water the mixture of oil and soap stock formed by said agitation, and thereafter separstingtrom the mixture by centrifugei force soap and the water which said oil and soap stock. IL-AYERS. 

